1. Technical Field
The inventive concept relates to a non-volatile semiconductor memory device and, more particularly, to a phase change memory device capable of reducing disturbance and a method of manufacturing the same.
2. Related Art
Semiconductor memory devices are classified into volatile memory devices and nonvolatile memory devices depending on retention of stored data in power off. DRAMs (Dynamic Random Access Memories) and SRAMs (Static Random Access Memories) are regarded as volatile memory devices and flash memory devices and EEPROMs (Electrically Erasable Programmable Read Only Memories) are regarded as nonvolatile memory devices.
Flash memory devices which are nonvolatile memory devices are generally used in electronic appliances such as digital cameras, cellular phones, or MP3 players. However, it takes a long time to program data in the flash memory devices or to read from the flash memory devices. New semiconductor devices as a substitute of flash memory devices such as MRAM (Magnetic Random Access Memory), FRAM (Ferroelectric Random Access Memory) or Phase-change Random Access Memory have been developed.
A phase change memory device as a substitute memory device uses phase change material which is mutually phase-changed between a crystalline state and an amorphous state by heat as a storage medium. Typically, a chalcogenide (GST)-based material which is comprised of germanium (Ge), antimony (Sb) and tellurium (Te) is used as the phase change material. The heat supply source for the phase change material is current and an amount of heat depends on the intensity of the supplied current and the current supply time. At this time, since the phase change material has a different resistance according to the crystalline state, the logic information depends on the resistance difference.
However, as integrity of the phase memory device is increased, the distance between the heating electrodes is decreased. When the heating electrode is heated by supplying the current so as to write the specific cell which the information is to be obtained from, the adjacent cell which the information has been already read from is affected by the heat disturbance. The heat disturbance causes errors in the output information processing procedure of the memory device. In particular, the heat disturbance more seriously occurs between phase change memory cells connected to the same bit line.